ST elevation myocardial infarction pre-hospital care

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

When symptoms of myocardial infarction occur, patients unfortunately often delay seeking medical attention. Ultimate survival depends largely on how fast a patient can receive care.

Symptom to Door Time

Prior to 2000, this delay of seeking medical attention was almost 3 hours in the United States, but as a result of public health education efforts, this delay has now been shorted to 1.5 to 2.0 hours. Patients often drive themselves to the hospital instead of calling 9-1-1. Further public health efforts appear to be warranted to urge patients to seek medical attention more quickly and to call for 9-1-1 to assure safe transport to the hospital.

Pre-Hospital Care

In some countries, such as France, physicians staff mobile intensive care units and pre-hospital care can begin in the ambulance. These pre-hospital therapies in the mobile intensive care setting include glycoprtein IIbIIIa inhibition (as was studied in the On TIME 2 study), unfractionated heparin, nitroglycerin, clopidogrel, oxygen and non-enteric coated aspirin. Pre-hsopital administration can speed the delivery of these agents by approximately 30 minutes, but transfer to the hospital should not be delayed by the administration of these agents. Pre-hospital therapy with aspirin, nitroglycerin and oxygen is common in the United States. The time to administration of a fibrinolytic agent can be shortened by 30 minutes with pre-hospital administration.

Role of First Responders Before the Arrival of Paramedics

In the United States, volunteers and fire fighters are permitted to initiate emergency care prior to the arrival of highly trained paramedics. These first responders can begin CPR and if adequately trained, can defibrillate the patient using an automatic external defibrillator (AED). Since the publication of data showing that the availability of automated external defibrillators (AEDs) in public places may significantly increase chances of survival, many of these have been installed in public buildings, public transport facilities, and in non-ambulance emergency vehicles (e.g. police cars and fire engines). AEDs analyze the heart's rhythm and determine whether the rhythm is amenable to defibrillation ("shockable"), as in ventricular tachycardia and ventricular fibrillation. This effort has been expanded to include laypersons as part of the Public Access Defibrillation (PAD) program in communities. This effort has been effective as well, particularly when deployed by community members with some training such as flight attendants and security personnel.

Steps to be Taken by Paramedics on Arrival at the Scene of a STEMI

If an Automated External Defibrillator (AED) is available the rescuer should immediately bring the AED to the patient's side and be prepared to follow its instructions should the victim lose consciousness. If possible the rescuer should obtain basic information from the victim, in case the patient is unable to answer questions once emergency medical technicians arrive (if the patient becomes unconscious). The victim's name and any information regarding the nature of the victims pain will useful to health care providers. Also the exact time that these symptoms started, what the patient was doing at the onset of symptoms, and anything else that might give clues to the pathology of the chest pain. It is also very important to relay any actions that have been taken, such as the number or dose of aspirin or nitroglycerin given, to the EMS personnel. Other general first aid principles include monitoring pulse, breathing, level of consciousness and, if possible, the blood pressure of the patient. In case of cardiac arrest, cardiopulmonary resuscitation (CPR) can be administered.

Emergency Services

Emergency Medical Services (EMS) Systems vary considerably in their ability to evaluate and treat patients with suspected acute myocardial infarction. EMS services are staffed by either volunteers, fire fighters, or highly trained paramedics. As a result in the variability in training, some EMS services provide as little as first aid and early defibrillation. Others employ highly trained paramedics with sophisticated technology and advanced protocols. Early access to EMS is promoted by a 9-1-1 system currently available to 90% of the population in the United States. Most are capable of providing oxygen, IV access, sublingual nitroglycerine, morphine, and aspirin. Few are capable of providing thrombolytic therapy in the pre-hospital setting.

With primary PCI emerging as the preferred therapy for ST segment elevation myocardial infarction, EMS can play a key role in reducing door to balloon intervals (the time from presentation to a hospital ER to the restoration of coronary artery blood flow) by performing a 12 lead ECG in the field and using this information to triage the patient to the most appropriate medical facility.In addition, the 12 lead ECG can be transmitted to the receiving hospital, which enables time saving decisions to be made prior to the patient's arrival. This may include a "cardiac alert" or "STEMI alert" that calls in off duty personnel in areas where the cardiac cath lab is not staffed 24 hours a day. Even in the absence of a formal alerting program, pre-hospital 12 lead ECGs are independently associated with reduced door to treatment intervals in the emergency department.

STEMI Management During Air Travel

Certified personnel traveling by commercial aircraft may be able to assist an MI patient by using the on-board first aid kit, which may contain some cardiac drugs (such as glyceryl trinitrate spray, aspirin, or opioid painkillers) and oxygen. Pilots may divert the flight to land at a nearby airport. Automatic external defibrillators are being introduced by some airlines, and they can be used by both on-board and ground-based physicians. If there is no pharmacotherapy provided by the airline, soemtimes other passengers will have in their possession cardiac medications that can be of use. If the patient is hypotensive, they should be placed in Trendelenberg position.

Wilderness First Aid

In wilderness first aid, a possible heart attack justifies evacuation by the fastest available means, including MEDEVAC.

2004 ACC/AHA Guidelines for the Management of Patients With ST-Elevation Myocardial Infarction (DO NOT EDIT)

Class I

"1. Prehospital EMS providers should administer 162 to 325 mg of aspirin (chewed) to chest pain patients suspected of having STEMI unless contraindicated or already taken by the patient. Although some trials have used enteric-coated aspirin for initial dosing, more rapid buccal absorption occurs with non–entericcoated formulations. (Level of Evidence: C)"

Class IIa

"1. It is reasonable for all 9-1-1 dispatchers to advise patients without a history of aspirin allergy who have symptoms of STEMI to chew aspirin (162 to 325 mg) while awaiting arrival of prehospital EMS providers. Although some trials have used enteric-coated aspirin for initial dosing, more rapid buccal absorption occurs with non–enteric-coated formulations. (Level of Evidence: C)"

"2. It is reasonable that all ACLS providers perform and evaluate 12-lead ECGs routinely on chest pain patients suspected of STEMI. (Level of Evidence: B)"

"3. If the ECG shows evidence of STEMI, it is reasonable that prehospital ACLS providers review a reperfusion “checklist” and relay the ECG and checklist findings to a predetermined medical control facility and/or receiving hospital. (Level of Evidence: C)"

Sources

• The 2004 ACC/AHA Guidelines for the Management of Patients With ST-Elevation Myocardial Infarction